The disclosure of Japanese Patent Application No. 2001-253872 filed on Aug. 24, 2001 including the specification, drawings and abstract are incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a control apparatus of an electromagnetic drive valve, and more particularly to a control apparatus of an electromagnetic drive valve which drives a valve body serving as an intake valve or an exhaust valve in an internal combustion engine on the basis of an electromagnetic force, and a control method of the same.
2. Description of the Related Art
Conventionally, as a related art, an electromagnetic drive valve provided with a rush adjuster, for example, as disclosed in Japanese Patent Laid-Open Publication No. 2000-24896 is known. A conventional electromagnetic drive valve is provided with a valve body serving as an intake valve or an exhaust valve in an internal combustion engine, and a mechanism for driving the valve body on the basis of an electromagnetic force.
The mechanism for driving the valve body on the basis of the electromagnetic force includes an armature, and an upper coil and a lower coil which are arranged apart from each other above and under the armature. The armature is held so as to be displaceable in an axial direction, and a lower end thereof is connected to the valve body via the rush adjuster.
In the mechanism in which no rush adjuster is provided, and the valve body and the armature can not be relatively displaced in length, there is a case that the valve body can not move to a full-close position due to an influence of thermal expansion and the like. The rush adjuster absorbs the influence of the thermal expansion and the like, and adjusts a relative position between the armature and the valve body so that the valve body can always move to a suitable position. Accordingly, in accordance with the electromagnetic drive valve provided with the rush adjuster, it is possible to always open and close the valve body in a suitable manner without being affected by the thermal expansion and the like.
Meanwhile, in the electromagnetic drive valve provided with the rush adjuster, there is a case that a position of the armature in an axial direction is offset to either upward or downward directions from a center of the upper coil and the lower coil in accordance with expansion and contraction of the rush adjuster. In this case, when uniformly applying an exciting current to both of the upper coil and the lower coil, an unnecessarily large electromagnetic force is generated between one coil and the armature, and an electromagnetic force generated between another coil and the armature becomes excessively small.
In the publication mentioned above, in order to solve the unbalance of the electromagnetic force, there is disclosed an art for reducing the exciting current supplied to the coil that is closer to the armature, while increasing the exciting current supplied to the coil that is away from the armature, in the case that the position of the armature is offset to either upper or lower directions from the middle position between the upper coil and the lower coil. In accordance with this art, it is possible to balance the electromagnetic forces generated between the armature and two coils so as to efficiently drive the electromagnetic drive valve, irrespective of the offset of the armature position.
However, the related art mentioned above consistently corresponds to an art for efficiently opening and closing the valve body in the case that the position of the armature deviates from a middle position, and does not correspond to an art for efficiently starting the electromagnetic drive valve under a condition where the position of the armature deviates form the middle position. Further, with respect to an efficient starting of the electromagnetic drive valve under such a condition, there still remained a room for further improvement.
The invention is made for the purpose of solving the problem as mentioned above, and an object of the invention is to provide a control apparatus of an electromagnetic drive valve which can efficiently start an electromagnetic valve in the case that a position of an armature deviates from a middle position.
A description will be given below of means for achieving the aforementioned abject and an effect thereof.
In accordance with an aspect of the invention, a control apparatus of an electromagnetic drive valve comprises a valve body which is provided in an electromagnetic drive valve, a valve shaft which is fixed to the valve body, an armature which slides along an axial direction of the valve shaft, a rush adjuster which adjusts a relative position between the valve body and the armature in an axial direction so that a state of zero-rush is established, an upper coil which is arranged above the armature so as to generate an electromagnetic force for attracting the armature closer, a lower coil which is arranged under the armature so as to generate an electromagnetic force for attracting the armature closer, and a starting current application portion which applies a staring current at first to either the upper coil or the lower coil, whichever is closer to the armature, at a time of starting the electromagnetic drive valve.